339dcd4233
git-svn-id: svn://svn.code.sf.net/p/loki-lib/code/trunk@157 7ec92016-0320-0410-acc4-a06ded1c099a
520 lines
16 KiB
C++
Executable file
520 lines
16 KiB
C++
Executable file
////////////////////////////////////////////////////////////////////////////////
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// The Loki Library
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// Copyright (c) 2001 by Andrei Alexandrescu
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// This code accompanies the book:
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// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design
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// Patterns Applied". Copyright (c) 2001. Addison-Wesley.
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// Permission to use, copy, modify, distribute and sell this software for any
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// purpose is hereby granted without fee, provided that the above copyright
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// notice appear in all copies and that both that copyright notice and this
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// permission notice appear in supporting documentation.
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// The author or Addison-Wesley Longman make no representations about the
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// suitability of this software for any purpose. It is provided "as is"
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// without express or implied warranty.
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////////////////////////////////////////////////////////////////////////////////
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// Last update: Mar 08, 2003
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#ifndef HIERARCHYGENERATORS_INC_
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#define HIERARCHYGENERATORS_INC_
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#define IS_TYPELIST(TList) TL::Private::IsTypelist<TList>
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#include "Typelist.h"
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#include "TypeTraits.h"
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#include "EmptyType.h"
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#include "MSVC6Helpers.h"
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namespace Loki
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{
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////////////////////////////////////////////////////////////////////////////////
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// class template GenScatterHierarchy
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// Generates a scattered hierarchy starting from a typelist and a template
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// Invocation (TList is a typelist, Model is a template of one arg):
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// GenScatterHierarchy<TList, Model>
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// The generated class inherits all classes generated by instantiating the
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// template 'Model' with the types contained in TList
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////////////////////////////////////////////////////////////////////////////////
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// VC 6.0 changes:
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// * Unit is no longer a template template parameter.
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// * For every concrete unit-template there must be a normal class containing
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// a nested-template class called In. In should only contain a typedef to the
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// concrete Unit.
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//
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// Using the originial library one would write something like this:
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// class Foo {};
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// template <class T> struct TestUnit {};
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// void Func(TestUnit<Foo>);
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// int main()
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// {
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// GenScatterHierarchy<Typelist<Foo, NullType>, TestUnit> obj;
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// Func(obj); // calls Func(TestUnit<Foo>)
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// }
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//
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// Using this port the code would become:
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// class Foo {};
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// template <class T> struct TestUnit {};
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// struct TestUnitWrapper
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// {
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// template <class T> struct In {typedef TestUnit<T> type};
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// };
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// void Func(TestUnit<Foo>);
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// int main()
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// {
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// GenScatterHierarchy<Typelist<Foo, NullType>, TestUnitWrapper> obj;
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// Func(obj); // calls Func(TestUnit<Foo>)
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// }
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//
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// Not very nice, i know :-(
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//
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// See "Metaprogramming VC++ - more of Loki ported" from Mat Marcus
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// (http://lists.boost.org/MailArchives/boost/msg20915.php)
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//
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// Update:
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// -------
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// The first version of GenScatterHierarchy did not work with typelists
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// containing equal types. The MSVC 6.0 erroneously complains about
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// inaccessible base-classes (error C2584).
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// This new version adds Dummy-classes to the left branch of the generated
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// hierarchy to workaround this VC-Bug.
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// It creates hierarchies like this:
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//
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// Holder<int> NullType
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// \ /
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//Holder<int> GenScatter<int> GenScatter<NullType>
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// \ \ /
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//VC_InaccessibleBase InheritFromTo
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// \ |
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//GenScatter<int> GenScatter<TYPELIST_1(int)>
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// \ /
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// InheritFromTo
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// |
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// |
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//GenScatter<TYPELIST_2(int, int)>
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//
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// Of course this version of GenScatterHierarchy generates a lot more
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// classes (5*n) than Alexandrescu's original implementation (3*n)
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//
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template <class TList, class Unit> class GenScatterHierarchy;
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namespace Private
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{
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template <class T, class U>
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struct InheritFromTwo : public T, public U
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{
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};
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template <int tag>
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struct GenScatterImpl;
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// Specialization for a general typelist
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template <>
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struct GenScatterImpl<TL::Private::Typelist_ID>
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{
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template <class T, class MetaFunctionWrapper>
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struct In : public GenScatterHierarchy<typename T::Head,MetaFunctionWrapper>
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{
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typedef
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InheritFromTwo < VC_InaccessibleBase<GenScatterHierarchy<typename T::Head,
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MetaFunctionWrapper>, typename T::Tail>,
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GenScatterHierarchy<typename T::Tail,
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MetaFunctionWrapper>
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> type;
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typedef VC_InaccessibleBase<GenScatterHierarchy<typename T::Head, MetaFunctionWrapper>,typename T::Tail> LeftBase;
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typedef GenScatterHierarchy<typename T::Tail, MetaFunctionWrapper> RightBase;
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};
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};
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// Specialization for a typelist with only one element
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template <>
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struct GenScatterImpl<TL::Private::AtomList_ID>
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{
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template <class T, class MetaFunctionWrapper>
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struct In : public GenScatterHierarchy<typename T::Head,MetaFunctionWrapper>
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{
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// for the last Holder-class no dummy class is needed.
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typedef
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InheritFromTwo < GenScatterHierarchy<typename T::Head,
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MetaFunctionWrapper>,
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GenScatterHierarchy<NullType,
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MetaFunctionWrapper>
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> type;
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typedef GenScatterHierarchy<typename T::Head, MetaFunctionWrapper> LeftBase;
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typedef GenScatterHierarchy<NullType, MetaFunctionWrapper> RightBase;
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};
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};
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// Specialization for a single type
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template <>
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struct GenScatterImpl<TL::Private::NoneList_ID>
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{
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template <class AtomicType, class MetaFunctionWrapper>
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struct In
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{
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typedef typename
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ApplyInnerType<MetaFunctionWrapper, AtomicType>::type type;
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typedef type LeftBase;
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typedef EmptyType RightBase;
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//typedef AtomicType::THIS_SELECTED bla;
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};
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};
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// Specialization for NullType
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template <>
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struct GenScatterImpl<TL::Private::NullType_ID>
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{
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template <class NullTypeList, class MetaFunctionWrapper>
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struct In
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{
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typedef EmptyType type;
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typedef type LeftBase;
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typedef type RightBase;
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};
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};
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} // end namespace Private
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template <class T, class Unit>
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class GenScatterHierarchy : public Private::GenScatterImpl
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<
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IS_TYPELIST(T)::type_id
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>::template In<T, Unit>::type
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{
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public:
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typedef typename Select
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<
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TL::Private::IsTypelist<T>::value, T, void
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>::Result TList;
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typedef typename Private::GenScatterImpl
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<
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IS_TYPELIST(T)::type_id
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>::template In<T, Unit>::LeftBase LeftBase;
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typedef typename Private::GenScatterImpl
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<
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IS_TYPELIST(T)::type_id
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>::template In<T, Unit>::RightBase RightBase;
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template <typename U> struct Rebind
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{
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typedef ApplyInnerType<Unit, U>::type Result;
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};
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};
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////////////////////////////////////////////////////////////////////////////////
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// function template Field
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// Accesses a field in an object of a type generated with GenScatterHierarchy
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// Invocation (obj is an object of a type H generated with GenScatterHierarchy,
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// T is a type in the typelist used to generate H):
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// Field<T>(obj)
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// returns a reference to Unit<T>, where Unit is the template used to generate H
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////////////////////////////////////////////////////////////////////////////////
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template <class T, class TList, class UnitWrapper>
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typename ApplyInnerType<UnitWrapper, T>::type&
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Field(GenScatterHierarchy<TList, UnitWrapper>& obj,Type2Type<T>* = (Type2Type<T>*)0)
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{
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return obj;
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}
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template <class T, class TList, class UnitWrapper>
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const typename ApplyInnerType<UnitWrapper, T>::type&
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Field(const GenScatterHierarchy<TList, UnitWrapper>& obj, Type2Type<T>* = (Type2Type<T>*)0)
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{
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return obj;
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}
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////////////////////////////////////////////////////////////////////////////////
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// function template TupleUnit
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// The building block of tuples
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////////////////////////////////////////////////////////////////////////////////
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template <class T>
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struct TupleUnit
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{
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T value_;
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operator T&() { return value_; }
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operator const T&() const { return value_; }
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};
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////////////////////////////////////////////////////////////////////////////////
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// class template Tuple
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// Implements a tuple class that holds a number of values and provides field
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// access to them via the Field function (below)
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////////////////////////////////////////////////////////////////////////////////
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namespace Private
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{
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struct TupleUnitWrapper
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{
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template <class T>
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struct In
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{
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typedef TupleUnit<T> type;
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};
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};
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}
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template <class TList>
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struct Tuple : public GenScatterHierarchy<TList, Private::TupleUnitWrapper>
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{
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};
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////////////////////////////////////////////////////////////////////////////////
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// helper class template FieldHelper
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// See Field below
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////////////////////////////////////////////////////////////////////////////////
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template <unsigned int i>
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struct FieldHelper
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{
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template<class H, class Unit>
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struct In
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{
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private:
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typedef typename TL::TypeAt<typename H::TList, i>::Result ElementType;
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typedef typename ApplyInnerType<Unit, ElementType>::type UnitType;
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enum { isConst = TypeTraits<H>::isConst };
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typedef typename Select
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<
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isConst,
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const typename H::RightBase,
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typename H::RightBase
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>
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::Result RightBase;
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typedef typename Select
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<
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IsEqualType<UnitType, TupleUnit<ElementType> >::value,
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ElementType,
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UnitType
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>
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::Result UnqualifiedResultType;
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public:
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typedef typename Select
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<
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isConst,
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const UnqualifiedResultType,
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UnqualifiedResultType
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>
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::Result ResultType;
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// Must be a template, don't know why.
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// If Do is not a template and H& is used as parameter
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// MSVC will give a linker error.
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template <class T>
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static ResultType& Do(H& obj, T*)
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{
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//typedef typename T::RightBase RightBase;
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//RightBase& rightBase = obj;
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RightBase& rightBase = obj;
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return FieldHelper<i - 1>::template In<RightBase, Unit>::Do(rightBase, (int*)0);
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}
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};
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};
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template <>
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struct FieldHelper<0>
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{
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template<class H, class Unit>
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struct In
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{
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private:
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typedef typename H::TList::Head ElementType;
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typedef typename ApplyInnerType<Unit, ElementType>::type UnitType;
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enum { isConst = TypeTraits<H>::isConst };
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typedef typename Select
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<
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isConst,
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const typename H::LeftBase,
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typename H::LeftBase
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>
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::Result LeftBase;
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typedef typename Select
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<
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IsEqualType<UnitType, TupleUnit<ElementType> >::value,
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ElementType,
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UnitType
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>
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::Result UnqualifiedResultType;
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public:
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typedef typename Select
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<
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isConst,
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const UnqualifiedResultType,
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UnqualifiedResultType
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>
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::Result ResultType;
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public:
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template <class T>
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static ResultType& Do(H& obj, T*)
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{
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LeftBase& leftBase = obj;
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return leftBase;
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}
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};
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};
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////////////////////////////////////////////////////////////////////////////////
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// function template Field
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// Accesses a field in an object of a type generated with GenScatterHierarchy
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// Invocation (obj is an object of a type H generated with GenScatterHierarchy,
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// i is the index of a type in the typelist used to generate H):
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// Field<i>(obj)
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// returns a reference to Unit<T>, where Unit is the template used to generate H
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// and T is the i-th type in the typelist
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////////////////////////////////////////////////////////////////////////////////
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/*
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template <unsigned int i, class TList, class UnitWrapper>
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typename FieldHelper<i>::template In<GenScatterHierarchy<TList, UnitWrapper>,UnitWrapper>::ResultType&
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Field(GenScatterHierarchy<TList, UnitWrapper>& obj, Int2Type<i>)
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{
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typedef typename GenScatterHierarchy<TList, UnitWrapper> H;
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return FieldHelper<i>::template In<H, UnitWrapper>::Do(obj, (int*)0);
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}
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*/
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template <unsigned int i, class TList, class UnitWrapper>
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typename FieldHelper<i>::template In<GenScatterHierarchy<TList, UnitWrapper>,UnitWrapper>::ResultType&
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Field(GenScatterHierarchy<TList, UnitWrapper>& obj, Int2Type<i>* = (Int2Type<i>*)0)
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{
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typedef typename GenScatterHierarchy<TList, UnitWrapper> H;
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return FieldHelper<i>::template In<H, UnitWrapper>::Do(obj, (int*)0);
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}
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////////////////////////////////////////////////////////////////////////////////
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// class template GenLinearHierarchy
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// Generates a linear hierarchy starting from a typelist and a template
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// Invocation (TList is a typelist, Model is a template of two args):
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// GenScatterHierarchy<TList, Model>
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////////////////////////////////////////////////////////////////////////////////
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// VC 6.0 changes:
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// see GenScatterHierarchy
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template
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<
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class TList,
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class Unit,
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class Root = EmptyType
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>
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class GenLinearHierarchy;
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namespace Private
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{
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template <typename TListTag>
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struct GenLinearHierarchyHelper
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{
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template<class TList, class Unit, class Root>
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struct In
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{
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typedef typename TList::ERROR_THIS_INSTANCE_SELECTED Result;
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};
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};
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template <>
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struct GenLinearHierarchyHelper<TL::Private::Typelist_tag>
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{
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template<class TList, class Unit, class Root>
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struct In
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{
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private:
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typedef typename TList::Head Head;
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typedef typename TList::Tail Tail;
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public:
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typedef typename
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ApplyInnerType2<Unit, Head, GenLinearHierarchy<Tail, Unit, Root> >::type Result;
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};
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};
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template <>
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struct GenLinearHierarchyHelper<TL::Private::NullType_tag>
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{
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template<class TList, class Unit, class Root>
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struct In
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{
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private:
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typedef typename TList::Head Head;
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public:
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typedef typename ApplyInnerType2<Unit,Head, Root>::type Result;
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};
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};
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template <class T, class U, class Root>
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struct Wrap
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{
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struct Dummy {};
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typedef typename T::Tail Tail;
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// create the hierarchy
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typedef typename Private::GenLinearHierarchyHelper
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<
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typename TL::Private::IsTypelist<Tail>::type_tag
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>
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::template In<T, U, Root>::Result TempType;
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typedef Private::VC_Base_Workaround<TempType, Dummy> type;
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// this is nothing more than a typedef to the created hierarchy (TempType).
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// But if we try to inherit directly from TempType VC 6.0
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// will produce a "Error C2516. : is not a legal base class."
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typedef typename type::LeftBase Base;
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};
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} // namespace Private
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// Trying to inherit from LinBase will result in "Error C2516. : is not a legal base class."
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// Private::Wrap introduces some levels of indirections which will
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// make the vc happy.
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template
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<
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class TList,
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class Unit,
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class Root
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>
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class GenLinearHierarchy : public Private::Wrap<TList, Unit, Root>::Base
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{
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ASSERT_TYPELIST(TList); // TList must not be NullType
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public:
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typedef typename Private::GenLinearHierarchyHelper
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<
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typename TL::Private::IsTypelist<typename TList::Tail>::type_tag
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>
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::template In<TList, Unit, Root>::Result LinBase;
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};
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} // namespace Loki
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#if defined (_MSC_VER) && _MSC_VER <= 1300
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#define FIELD(Obj, Nr) \
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Field(Obj, (Int2Type<Nr>*)0)
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#else
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#define FIELD(Obj, Nr) \
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Field<Nr>(Obj)
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#endif
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////////////////////////////////////////////////////////////////////////////////
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// Change log:
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// June 20, 2001: ported by Nick Thurn to gcc 2.95.3. Kudos, Nick!!!
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// September 16, 2002: Fixed dependent template, using "::template" syntax. T.S.
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// Oct 24, 2002: ported by Benjamin Kaufmann to MSVC 6
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// Dec 08, 2002: Fixed problems with MSVC6-Version of GenScatterHierarchy when
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// used with typelists containing equal types. B.K.
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// New Version is ugly :-(
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// Dec 08, 2002: Interface changed for Field-Function. The old version does not
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// work correctly due to the "Explicitly Specified Template
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// Functions Not Overloaded Correctly"-Bug
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// (Microsoft KB Article - 240871). B.K.
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// Mar 08, 2003: New transparent workaround for Field-Functions. The FIELD-Macro
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// is no longer needed. B.K.
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////////////////////////////////////////////////////////////////////////////////
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#undef IS_TYPELIST
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#endif // HIERARCHYGENERATORS_INC_
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